Property And Equipment - Gross Components Of Property And Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,938,154	$ 2,948,907
Vessels
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,343,162	2,349,752
Vessels | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years
Vessels | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
ROVs and Trenchers
Property, Plant and Equipment [Line Items]
Property and equipment	$ 257,274	263,968
Estimated useful life	10 years
Machinery, Equipment and Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 337,718	$ 335,187
Machinery, Equipment and Leasehold Improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Machinery, Equipment and Leasehold Improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	15 years